At low CSK levels, as is the case in patients with ER<sup>+</sup> breast cancer resistant to endocrine therapy and with the poorest outcomes, the p21 protein-activated kinase 2 (PAK2) becomes activated and drives estrogen-independent growth.
In this study we report that OPN induces alpha(v)beta(3) integrin-mediated c-Src kinase activity in both highly invasive (MDA-MB-231) and low invasive (MCF-7) breast cancer cells.
Our findings indicate that PTP1B is the primary protein-tyrosine phosphatase capable of dephosphorylating c-Src in several human breast cancer cell lines and suggests a regulatory role for PTP1B in the control of c-Src kinase activity.